Manuscript received November 11, 2005; revised July 7, 2006 and April 24, 2007; accepted April 28, 2007. The editor coordinating the review of this paper and approving it for publication was A. Yener. This work was supported by NSF Grants ANI 02-05330, CCR 03-11311 and CCF 04-47613, ARL/CTA Grant DAAD 19-01-2-0011, and the Scientific & Technological Research Council of Turkey Grant 106E018; and was presented in part at the IEEE International Conference on Wireless Networks, Communications, and Mobile Computing, Maui, HI, June 2005.
Sreejith SreekumarBikash Kumar DeySibi Raj B. Pillai